44 



AMERICAN MESOZOIC MAMMALIA 



lOi&i 



1034-i . (6) Mylohyoid groove distinct 



on inside of lower jaws. 



(7) Angle of lower jaw with- 

 out distinct inflection. 



(8) Condyle of lower jaw near 

 or below horizon of teeth. 



(9) Condyle vertical or round, 

 not transverse. 



The generalized members of this 

 order were doubtless the forms 

 from which the modern special- 

 ized Insectivores and Marsupials, 

 at least, were derived." 



As a matter of historical in- 

 terest, not detracting from the 

 importance of Marsh's recogni- 

 tion of the group for the first 

 time, it may be noted that (i), 

 while probably true, was not 

 based on good evidence, that (2) 

 and (4), as he later recognized, 

 are open to exception, and that 

 (3) and (8) are not strictly true. 

 As was noted in dealing with 

 the Triconodonta, it is uncertain 

 just how many Jurassic mammals 

 were intended to be included in 

 the Pantotheria. The natural in- 

 ference from the arrangement of 

 his paper of 1887 would be that 

 he included all Jurassic mam- 

 mals except the Allotheria. There 

 can, however, be no doubt that the 

 order was primarily based on the 

 Dryolestidae. Although he specifi- 

 cally refers the Dromatheriidae 

 to the Pantotheria, these, the tri- 

 conodonts, and the symmetro- 

 donts are excluded by his defini- 

 tion. In 1887 his views as to affinities were modified somewhat, as he then saw no mar- 

 supial characters in the order and considered it as possibly related to the Insectivora. 

 Among forms now referred to the order. Marsh recognized the families Dryolestidae, 

 "Diplocynodontidae," and Paurodontidae. In 1879 he had created a family Stylodon- 



J. 



B 



tli,51 



Fig. 21. Mesozoic mammals. Last upper premolars, i, Pria- 

 codon. 2, Peralestes. 3, Melanodon. 4, Herpetairus. 5, Do- 

 codon. 6, Gypsoniciops. Not to scale. 



